Recently, a tire with an improved wear resistance without losing low heat buildup is required as a heavy duty pneumatic tire used in a truck, a bus or the like from a viewpoint of low fuel consumption and a lifetime of the tire.
In this regard, there may be employed a method wherein a rubber composition compounded with an increased amount of carbon black as a filler or a rubber composition using carbon black having a smaller particle size is used in a tread of a tire in order to improve the wear resistance of the tire. In this case, the wear resistance of the tire is indeed improved, but the low heat buildup of the tire is drastically deteriorated and thereby fuel economy of the tire gets worse.
Also, there may be employed a method wherein a glass transition point (Tg) of a rubber component of a rubber composition used in a tread is raised in order to reduce a wear energy. In this case, the wear resistance of the tire is also indeed improved, but the low heat buildup of the tire is drastically deteriorated and thereby the fuel economy of the tire gets worse.
On the other hand, dispersibility of carbon black as a filler can be improved by using in a tread of a tire a rubber composition using as a rubber component a butadiene-based polymer formed by modifying its terminal to improve the wear resistance of the tire (see JP-A-2005-41975). In this case, there is, however, a problem that the low heat buildup of the tire is also deteriorated.